1. Field of the Invention
The invention relates to a process for controlling switching or shifting processes in automatic gears for use in drivelines of vehicles with a drive motor, especially in the form of a combustion engine, individually with the specified features; further, a gear control device.
2. Description of the Related Art
The current trend in vehicles toward a greater space offering, more comfort, a better acceleration and deceleration behavior, for reasons of safety in all traveling condition, as well as the increasing importance of environmental protection aspects, means more demand on the design of drivelines in combustion engine vehicles, an improvement of the energy conversion, from the energy chemically bound in the fuel to the mechanical drive energy required on the vehicle wheels. Besides the improvement of the individual components, the main emphasis there lies on achieving possibilities of fuel saving by optimizing of the driveline by appraisal of the total system, especially of the cooperation between the individual motor and gear components. This demands an optimal adaptation of the gear transmission to the characteristics of the combustion engine, also called motor characteristics, in order to ensure in all traveling conditions and operation of the vehicle a correspondingly favorable fuel consumption value and optimal driving properties. It is well known that the driving performance, the fuel consumption as well as the useful life of the driveline can be considerably influenced by corresponding switching programs of automatic gears. From the state of the art a large number of different switching programs are known which can do justice to the most diverse requirements. The aim there is to achieve a limitation of the working range of the combustion engine to the economical operating points. In the simplest case this is possible by the stipulation of pedal-position dependent fixed switching speeds. There hitherto for reasons of simplicity there was used as switching speed the output turning rate of the gear, which can be assigned in each gear to a certain motor turning rate and which is proportional to the traveling speed. If there the upper limit speed is exceeded, a switching up is performed; if the lower limit speed is fallen below, a switching downward is performed. In traveling operation it is steadily checked whether for the actually traveled condition in actual operation the switching speed is reached or exceeded. If this condition is fulfilled the switching operation is performed. Since during a switching process to be performed, however, also power is transferred, so that there is present the possibility of a further acceleration of the vehicle during the gear change, the motor speed that sets in after the switching process will very much depend on what acceleration has arisen during the switching operation. Thus, it is possible that with an empty vehicle a great acceleration occurs and the motor speed after the switching, therefore, is comparatively high, while with a loaded vehicle a low acceleration occurs and the motor speed therefore is comparatively low. In the first case, with an empty vehicle, because of the necessarily high rate of rotation after the switching, a use disadvantage will occur, while with a loaded vehicle only is the after-the-switching use-optimal. For the avoidance of this disadvantageous effect, therefore, switching programs were developed in which the switching speeds are dependent not only on the load stages, but additionally on the longitudinal acceleration of the vehicle. Such a switching process is described, for example in the publication DE 195 16948 A1. In the process disclosed in this publication the switching-over occurs in dependence on acceleration. Thus depending on the requirements or traveling resistance, switching is done at lower or at higher off-drive or motor speeds, according to whether there is to be preferred a low fuel consumption or a sufficient acceleration. For the switching itself the acceleration of the vehicle or its deceleration is determinative. There, the two following limitsxe2x80x94traveling states or accelerationsxe2x80x94are always taken into account:
1. low vehicle load on flat or precipitous terrain=high vehicle acceleration and
2. high vehicle load on rising terrain=low vehicle acceleration.
In the first-mentioned case there is yielded then a high vehicle acceleration at low off-drive speeds. A switching-up of the gears, therefore, can occur early already, at a relatively low motor speed, which leads to a lowering of the fuel consumption. For the same reason also the switching-back of the gears occurs with less deceleration at a low motor speed. In the second case a greater motor performance is required, for which reason the switching-up occurs only at a relatively high off-drive speed that corresponds to a high motor speed. In dependence on the measured vehicle acceleration or deceleration the switching-up or switching-down of the gears occurs smoothly between these two traveling states, i.e., within a switching speed range. The switching speed range itself, furthermore, is dependent on the load conditions: with heavier loads, therefore, the switching takes also place at a higher speed.
With this switching program it is achieved that high accelerations lead to a switching-up at lower traveling speeds; the operating point of the motor, i.e., of the combustion engine, is therefore shifted early into a use-favorable range. Simultaneously, through the lower rate of rotation that follows the switching-up, the available motor performance is less. The two effects together lead to a reduction of the fuel consumption. The motor performance thereby limited at high accelerations is there only a desired side effect, which protects the passengers from inadmissible acceleration with empty vehicle. Also in the case of Kick-Down the maximally available power is always attainable, since an upshift does not occur until the regulating speed has been reached.
The designing of such an acceleration-dependent switching program occurs by means of standardized travel maneuvers in the computer. The necessary data on the admissible connection speeds and on the upper limit speeds are obtained there from the motor characteristic diagram. As further parameters there are needed the data of the driveline (converter characteristic curves, axial translation, etc.) and the vehicle data (mass, travel resistances). As the result of the design there is obtained a data set for the switching program, which in the normal case is then deposited in the control of the gear and with which the desired connection speeds are to be achieved without the occurrence of any gear oscillations. An essential disadvantage lies in that the optimal functioning of such an acceleration-dependent switching program requires the individual attuning to the circumstances of the particular driveline, i.e., for example, the axial translation, the existing tire dimension, the type of converter used, etc., from which there results a multiplicity of switching program variants that are expensive to develop and to govern. Also the delivery of the gear often cannot occur with an optimal switching program, whereby complaints and supplementary work are preprogrammed. The frequency of the arising of this type of problems will certainly increase in the future, since the vehicle manufacturer himself as a rule still is ignorant at all the vehicle data for the gear and, in the extreme case, even orders individual gear components separately. A further substantial disadvantage of such a switching program lies in the arising of clear scatterings of the connection speeds, especially in gears with converter operation and especially when the progression ratio is very high.
Underlying the invention, therefore, is the problem of further developing a process for the control of an automatic gear for use in drivelines of vehicles with a combustion engine and preferably an integrated CAN-Bus in such manner that the disadvantages mentioned are avoided. In particular the process for the control of a switching operation is to make possible a switching program which no longer involves any attuning to a certain driveline. The multiplicity of the possible switching program variants is to be reduced to a minimum. The gear itself is to be equipped, on delivery already, with a switching program which from the first setting into operation makes possible an optimal functioning of the automatic gear in association with the combustion engine. Also, severe scatterings are to be avoided between the connection speeds to be reached under the same conditions.
According to the invention the disadvantages mentioned are avoided by a so-called real-time prognosis of the connection speed to be achieved in the target gear. The conventional sets of data, in conventional switching programs for load-conditions, acceleration-, and speed-dependent switching speeds are now replaced by the characteristic diagram of the motor, in particular of the combustion engine. As a rule it is a matter here of a power/speed diagram or of a torque/speed diagram. The motor characteristic diagram either can be generated directly in the gear control and deposited there, or it can be put in or read-in and stored.
Preferably the process of the invention is used with an integrated CAN-bus. In this case the motor characteristic diagram is already deposited or stored in the CAN-Bus, and it is possible to fall back upon it from the gear control. Thereby no data are any longer to be preset for the switching points and the control of the gear adapts itself. As motor characteristic diagram, here it is possible to use a motor performance-motor speed characteristic diagram or a so-called torque/speed characteristic diagram of the motor. There, insofar as possible, vehicle-specific data are taken from the CAN-Bus or computed from measurement values that are available there and that can be called in.
The solution according to the invention makes available an automatic gear with a switching program which requires no individual attuning to a certain driveline. The gear can be delivered with a switching program already, and in an initial setting-in-operation it passes into an optimal functioning, since the requisite data are automatically generated from the motor characteristic diagram.
The process for the control of the switching process proceeds according to the invention in the following steps:
a) Detection or determination of the movement-dynamic magnitudes at a certain time point to 
b) Determination of the theoretically achievable connection speed of the drive mechanism, especially of the combustion engine, n_mot_pr_h in the target gear gtgt=gact+n with n=1, in which for gear systems with a greater number of gears, several target gears can also be investigated so that, for example there holds n xcex5(1, 2, 3), or n_mot_pr in the actually inserted gear gact at the time point t=to+tshift 
c) Comparison of the prognosticated connection or target speeds with stipulatable limit speeds and decision about
c1) the carrying-out of a switching operation and
c2) the type of switching (upshift or downshift) in dependence on the result of comparison.
For a switching process to be undertaken, in the first process step at the time point to, at least the following dynamic magnitudes are determined:
n_motxe2x80x94motor speed
n_abxe2x80x94output speed of the gear
Pedxe2x80x94gas pedal position
Ped_brxe2x80x94brake pedal position
a magnitude (v or iaxial, xcex93dynamic together with the driven speed (n_ab) characterizing the raveling speed at least indirectly.
When the gear system is used in vehicle with an integrated CAN-Bus as communication interface between different control arrangements or with a similar system, these magnitudes can be in part derived from the latter; in part, however, special sensors are required. There the magnitudes motor speed, gas pedal position, brake pedal position, and traveling speed can be taken from the CAN-Bus as source, while for the detection of the output speed of the gear, as a rule, a corresponding arrangement is necessary at the gear system output. The above-mentioned magnitudes represent there the magnitudes required for the functioning of the process of the invention. In order to do justice to additional demands, for example the avoidance of unnecessary switching operations and the making possible of a fuel-saving traveling behavior with sufficient traveling performances, additional physical magnitudes can be drawn upon for the gear control. These magnitudes, as a rule, are also available over the CAN-bus or can be determined via magnitudes available over the CAN-bus. To these there belong:
P_motxe2x80x94motor performance
bexe2x80x94characteristic diagram of the specific fuel consumption
Bxe2x80x94injection amount
Characteristic diagram of the specific emissions
pxe2x80x94barometric pressure
Psi_Pointxe2x80x94yaw angle speed
In the other case, i.e., in use of vehicles without such a communication interface, for the detection or determination of the individual magnitudes corresponding arrangements are to be provided, preferably in the form of sensors.
The determination of the theoretically achievable connection speed of the drive machine, especially of the combustion engine n_mo_pr_h in the target gear ggtg=gact+n or n_mot_pr in the actually set-in gear gact at the time point t=t+tshift occurs continuously at time intervals of ca. 1 to max. 10 milliseconds, which are dependent on the capacity of the processor used in the control, especially also its clock frequency. The switching duration tshift fluctuates slightly and amounts, for example, to between 1 and 2 s. For the concrete establishment of the switching duration it is possible to proceed from a basic advance value, which on undertaking of a large number of switching operations can be modified or adapted on the basis of the result present at the end of the switching process. The modification can occur there adaptively, through a regulation or a combination of both processes. In this manner of procedure it is reasonable to resort to a correction value which describes the deviation of the actually setting-in speed from the predicted connection speed. Thus, for example, for each executed switching the correction value can be determined from the prognosticated connection speed of rotation, and from the setting-in connection speed of rotation, it being possible to deposit this latter in an experiment table.
Another possibility, with the reproducibility of the switching time, lies in realizing an improvement by taking into consideration the underlying physical interrelationships and calculating the theoretical switching duration. Thus, for example, there can likewise be included the kinetic excess energy of the motor which is transformed into heat during the switching operation.
With the limit speeds mentioned under process step c) it is a matter of the generally maximally and minimally admissible two curves of the motor speeds, which establish an upper speed limit range and a lower speed limit range in the motor characteristic diagram, and therewith bound its working range.
The establishment of the stipulated limits for the switching speeds (lower curve of the minimally admissible switching speed and upper curve of the maximally admissible switching speed) occurs by automatic generation from the motor characteristic diagram, in dependence on characteristic points in this. The generation occurs over the gear control. There the reference to the load stages in the process of the invention is abandoned, since the access to the gas pedal position can occur stagelessly in the use in vehicles with integrated CAN-Bus or a similar communication interface between individual control devices over the so-called CAN-Bus. The limit curves for the upper and lower speed limit range can therewith be generated by stageless curves. By the term CAN there is understood there the so-called CAN-Bus, a conduction pair which, like a nerve path, connects the individual control devices in the vehicle with one another. This conduction pair serves there primarily for the communication of the control devices among one another. The individual control devices are cross-linked there by a communication system which is capable of conducting the necessary data exchange.
In the so-called CAN-Bus, for example, one control device takes up the information for the speed (rate of rotation), transforms this into a form readable for all the other control devices and sends this message to the CAN-Bus, from where it can be called in for all the other control devices.
In the other case, with backing of the motor characteristic diagram in the gear control by reading-in of the corresponding data or programming, i.e., non automatic access to the characteristic data with coupling of the gear control with other control arrangements, in the use in vehicles without communication interfaces, the limit speeds are generated or derived in the same manner from the motor characteristic diagram stored in the gear control.
In the simplest case so-called basic limit speed ranges are established which for the achievement of additional advantageous properties have boundaries that are reducible and/or shiftable with respect to the basic speed limit range. The upper basic speed limit range, i.e., the so-called upshift line, is established there by at least three points Ph1 to Ph3. In order to establish the coordinates for upshifting or downshifting, values in the form of factors, for example Kh1, kh2, kh3 and kr1, kr2, are to be determined in such manner that these are valid for virtually any motor. The establishing of the factors there can occur with the aid of a large number of real motor characteristic diagrams, and can be ascertained according to statistical criteria. The individual points are then determined as follows:
point Ph1=(speed (rpm)nh1=kh1xc3x97nregulated M on full load line)
point Ph2=(nr2=max{kh2xc3x97(nregulatedxe2x88x92nmin)+nmin; nr2xc3x97ispr},; M is yielded by the intersection with the line of a certain specific fuel consumption be, for example be=230 g/kwh)
point Ph3=(nh2=max{kh3xc3x97nh2; nr3xc3x97ispr}; M=0)
For the determination of the lower basic speed limit range likewise at least three points Pr1, Pr2 and Pr3 are necessary.
Pr1 corresponds there to the bend-off point of the full load line with constant motor moment, when the full load line is run through downward-falling speeds.
Pr2 is yielded from the intersection of the full-load line with the characteristic curve (line) for the specific fuel consumption which was used for the establishing of the second point Ph2 or this is determined from the relation nr2=kr2xc3x97nr1.
Pr3 is yielded from the dropping of the plumb line from point Pr2 onto the speed axis.
As additional requirement, the range established by the basic speed curves must have further, for the avoidance of gear oscillations, a speed ratio greater than the maximal gear leap ispr. For this reason there holds:
nh3/nr3 greater than ispr.
This leads to the above-mentioned conditions for nh2 and nh3 by the stipulation of which gear oscillation are to be dependably avoided and the thus-defined working range of the motor should lead to a faultless switching behavior, in which the demands of a use-favorable operation are also covered.
For the achievement of advantageous properties additional restrictions of the working range of the combustion engine by change of the basic limit speed range are possible. A restriction of the working range of the combustion engine is conceivable in respect to the use-favorable behavior in dependence on traveling dynamics and on the wish of the driver. The consideration of these magnitudes, however, presumes additional sensors for their detection. If these sensors drop out, there remains preserved, however, the basic limit speed range and therewith the basic working range of the combustion engine. The bounding-in of the working range can occur, for example, inter alia in dependence on the following magnitudes: The bounding-in of the working range can occur, for example, inter alia in dependence on the following magnitudes:
The bounding-in of the working range can occur, for example, inter alia in dependence on the following magnitudes:
Gas pedal speed and/or
Vehicle mass and/or
Roadway gradient.
With a high gas pedal speed, i.e., the desire for more power, the admissible speed range should be shifted to higher admissible speeds with respect to the working range bounded by the basic limit speeds. Thereby it becomes possible that for the driver, who has shown impatience because his gas pedal movement, an increased performance readiness is made available, as the lower motor speeds can no longer be used.
As a further criterion the vehicle mass can bring about a displacement of the working range. An empty vehicle, therefore, operates with working range shifted to the left. If the vehicle is full, the working range is shifted to the right in the torque/speed characteristic diagram of the motor. A statement similar to the one for the vehicle mass also holds for the roadway gradient.
Since the process of the invention is used preferably in automatic gears of vehicle drivelilnes which are equipped with a CAN-bus or a similar system, the control device of the gear control can resort to the motor characteristic diagram stored in the CAN-bus. The gear control then generates, on first setting in operation of the driveline, at least the basic limit speeds in the motor characteristic diagram and therewith bounds the working range for the cooperation motor-gear cooperation. In the event that further advantageous properties of the switching processes to be undertaken (for example the execution of switching operations only in the range most favorable for use) are to be achieved, this can likewise be taken into consideration in the generating of the limit speed ranges. The corresponding algorithm for automatic generation of the basic limit range or of the possible restrictions of this range is a component of the gear control and is likewise included with delivery of the gear and of the appertaining control device. The motor characteristic diagram restricted in this manner with respect to the working range can then be deposited in a storage unit of the gear control and/or in the CAN-bus. Further, in the gear control there is deposited the algorithm for the decision on the performance and for the choice of the type of switching process to be realized, which (process) is continuously delivered. The corresponding input magnitudes to be considered, as already stated, are largely taken from the CAN-bus or fed to the gear control via corresponding couplings with the detection arrangements required therefor. The gear control system further has, for the realization of the process of the invention, a computing arrangement which determines the hypothetically attainable connection speeds in the target gear to be set in and/or the gear still present in the case of non-occurring switching. The calculating arrangement is coupled with a comparison to which at least the calculated magnitudes and the limit speeds for the processing can be fed. In correspondence to the result of the comparison at least one control magnitude is generated and issued for the setting members to be actuated for the gear change to be implemented. The gear change is executed or is not executed. The calculating arrangement for the determination of the hypothetically attainable connection speeds and the calculating arrangement for the setting of the limit speed ranges can be comprised in one component, but they do not have to be. The further processing of the control magnitude or control magnitudes for the governing of the setting members to be actuated for the gear change depends, there, on the type of gear, of construction, and of setting arrangements to be actuated and it lies therefore within the range of competence of the responsible specialist.